沙漠化逆转过程中沙地土壤碳积累与植被恢复的响应研究

After many years of vegetation construction, the desertification land in China has been significantly reversed. Mobile sandy land is a special component of Terrestrial ecosystem, It has the characteristics of low productivity, vulnerability and harmfulness. Artificial forest vegetation measures as an important way of desert control in northern China, it plays an important role in regulating the development of soil carbon pool and maintaining carbon balance. Study on the coupling mechanism between vegetation restoration process and soil carbon process in the convective sandy land, can provide theoretical guiding significance for maintain and enhance the capacity of soil carbon sequestration in sandy soil under the background of global change..This project taking Salix and Hedysarum mongolicum artificial shrub forest in Inner Mongolia Muus sandy land as the research object, at different stages of vegetation restoration, test the characteristics of plant community, soil carbon pool structure, carbon input and output process and microorganism ,analysis the dynamic evolution of soil carbon pool and its structure during the solidification process of mobile sand, and evaluate the stability. From the process of soil carbon budget and plant coupling, stady the effects of vegetation restoration on the development of soil carbon pool and the dynamic process of carbon budget in the sandy soil.,and using Biome-bgc ecosystem model, study the change rule of soil carbon pool and carbon budget with the process of plantation restoration，further reveal the coupling mechanism between vegetation restoration and soil carbon processes.

经多年的植被建设，我国土地沙漠化出现明显的逆转成效，其中沙地植被恢复效益最为突出。土流动沙地是陆地生态系统中生产力低，脆弱性和危害性最特殊组成部分。人工林植被措施一直是治沙重要途径，对固定流沙、促进土壤碳库的发育、维持碳平衡发挥重要的生物调节作用。对流动沙地植被过程与土壤碳积累过程耦合机制的研究，在全球变化背景之下维持和提高沙地土壤碳汇能力，增汇经营具有重要的理论指导意义。.本项目以内蒙古毛乌素沙地杨柴、沙柳人工固沙灌木林为研究对象，在植被过程的不同阶段，对植物群落特征、土壤碳库结构，碳输入输出过程及微生物进行测试，分析流动沙地固化过程中土壤碳库各组分及结构动态演变规律，评价其稳定性；揭示人工林植被恢复过程对沙地土壤碳库和碳收支动态过程的影响机理，用Biome-bgc生态模型，模拟研究人工林植被过程中土壤碳库及碳收支连续变化规律，进一步揭示植被过程和土壤碳积累过程之间的耦合机制。

本项目在我国北方沙漠化持续逆转、气候变化和“双碳目标”等大背景下，开展毛乌素沙地植被恢复过程中土壤碳积累、土壤碳输入和输出特征分析，阐明沙地土壤碳积累与植被恢复的响应机制，基于模型预测人工林植被恢复过程中土壤碳动态变化规律。研究结果如下，（1）沙地人工植被建植及其持续恢复促进了土壤有机物的积累，为土壤碳积累创造了良好的物质基础。随着造林年限的增加，杨柴、沙柳灌木林土壤中根系生物量、地表枯枝落叶量持续显著增加，且根系中死根量占比逐渐提升，生长30年的杨柴、沙柳灌木林地下根系中死根量达到20%-35%。枯枝落叶和死根是沙地土壤有机碳的重要物质来源。（2）沙地人工植被恢复显著促进了土壤碳库的可持续发育，碳库活度在表层土壤中最高。杨柴、沙柳人工灌木林随恢复年限增加土壤固碳量持续增强，且在表层0-10cm含量最高。以杨柴灌木林为例，土壤表层0-10 cm易氧化有机碳（DOC）、微生物生物量碳（MBC）和水溶性有机碳（ROC）对恢复演替响应较为敏感，且含量逐渐升高，10cm以下则变化缓慢。（3）沙地人工植被恢复增强了土壤呼吸作用，提高了碳排放贡献。枯枝落叶、根系的持续积累和微生物群落的发育是土壤呼吸的直接驱动因子。异养和自养呼吸分别占土壤总呼吸的76.32%和23.68%。以恢复30a杨柴林为例，年土壤呼吸碳通量为476.98 gC·m-2，与未造林流动沙地相比，增加了6.68倍。（4）沙地土壤呼吸驱动因子贡献。土壤有机物质含量、土壤微生物数量的增加、凋落物及地下根系生物量的持续积累是沙地土壤呼吸碳排量提高的主导因素。（5）沙地生态系统碳汇管理警示。毛乌素沙地人工植被恢复促进了土壤有机碳库发育，同时也加强了土壤呼吸作用，加快了土壤向大气排放二氧化碳的进程。碳排放量的持续增加必然导致土壤碳库的损失，这对我们今后加强沙地灌木林的经营来实现增汇给出了警示。通过对灌木林地上植被进行复壮增产提高固碳量，同时减少对沙地土壤的干扰和破坏，维持土壤碳库的稳定和可持续发展。